Gear-cutting apparatus



March 24, 1931. E Ll FTCKETT GEAR CUTTING APPARATUS Filed March 15. 19294 i III.

ATTRNEY Patented Mar. 24,y 1931` unir-ae STATES PATENT-,OFFICE v OF NEW'YORK y ERNEST L. EIcKETT, 0E YEITCHBUEG, MASSACHUSETTS, AssIGNoaiEfYMEsNE ASSIGN- MENTS, To scURLocK `GEAR CORPORATION,

0E NEWYORK, N. Y., A. coEPoEATroN GEAR-CUTTING ,rirramiuUs` The presentinvention has for an object to provide an'improved gear cutting machine.The invention has been'developed in connectionvvith the design of amachine of the general character of' thatshown in myprior applicationfor Letters Patent for machine` for cuttingspiral bevel gears, Ser.No.-98,901,

` filed March'l', 1926; and for-convenience of disclosure such anembodiment will be more 10 kparticularly described, `but it will beunderof a toothed cutter `which rotates in'synchronismfwith the workblank andis fed-along the face of the blank, it is necessary that therotation ofthe cutter be controlledin accord- 20 anceiboth 7with therelative number of teethl on the cutter and to be cut on the blank andalso in accordance with the angle of the teeth and the rate of feed ofthe cutter along they s face of the blank. When cutting gears, the

f .25 teeth of which follow an Arehimedean spiral,

the feed of the cutter and the rate of rotation` of the cutter and theblank may remain con stant during the Whole of the cutting operation,but when it is desired to. cut a spiral *3 bevel gear on, for example; alogarithmic yspiral or an involute spiral7 variation must be obtained. v

The calculation of the ratio .of drive for the cutter and work spindlesin which the '35 speed of drive of both is taken care of in one set ofchange speed gears is somewhat complicated and involves somewhattroublesomeAIA calculation both to obtain the desired ratios accuratelyand also to obtain a ratio which 4 `can be readily obtained by gears ofconven- The present invention provides an arrangement whereby the changespeedr ient sizes.

f gears can be of the ratio of the number of teeth in the cutter andwork respectively and 45 the additional rotation of the cutterand va`riation in the speed of rotation of the cutter can be obtained bysuperimposing an additional motion of rotation onto the cutter v througha dilferential mechanismI By this f 50 arrangement the two motions whichare, 1`n-` ell'ect, added together to rotate the cutter at the necessaryspeed can both be easily calculated; and obtained rthrough simplemechanisms,

The Inature and objects of the invention f f will be'better understoodfrom thefdescription of an illustrative embodiment forthe purpose ofwhich description reference should be had tothe accompanying drawings inWhich- Figure l is ay detail sectional view of a portion off'a cutterdriving mechanism embody ing the invention, and g 1 Figure@r is a bottomlplan' view of a cam andrack mechanism. z

The apparatus' shown `fory the purposes of illustrating the,principlesof therinvention comprises a cutter spindle 5 arranged tocarry-a gear cutter 6`-or `operating upon* a ygear blankl 'suitablyrotated in the machinef The cutter spindle; is rotatably mounted in acarriage -Sby whichr it is moved across the face of the gear blank anditis ydriven th-rougha differential mechanism 10 actu ated from v'twoysources, the actual rotation of the cutter dependingupon theresultantof these two actuations. 7 'y l As-shown, thel dilerential mechanismcomprises a' planet Acarrier12 rotatably mounted fon thecutterspindle-and carrying' planet?? pinions 13 engaginga driven gear 14"keyedto the spindleand ay sun gear 15 loose on the indie Aand havingy asleeve16 extending ownvvard'ly thrognthe base of the car-y actuated riagef"The "f'planeti carrier is throughaivorm wheel18a'ndworm 19 on thesplinedshaft 205 theworn'i vwheel beingdrivenf-'at l:a ratev of speeddepending upon the` Srfrate of `V`rotatioliof fthe'blank and thev'relative number jo'ff-teetli onfithe blank and cutterbut.ViY"inelepeiden't'f'of the character ofv'spifraliorfthe angle'ef the teethof the gear to be-f'eut." -fThe rgear v15 is'ac'tua'ted through"agQarJQr keyed to 'the lower'lend 'of thek Sleeve 16 landfe'ngaginglarelatively stationary rack 22 mounted Jin?- the f 'frame lof themachine.

`The 'pitch diameter of the gear-'21 isrequal to tlhptch 'diameter -ofthe-gear ,cutter' and ".-the'rak 'Qlfrnd 'the gear rblanlcto be cut vare""011" OJPOSte fSd'S 'of the. axis ofi the 'spindle l' ASi) thusproviding the desired motion through the differential. Y

If the rack 22 is held stationary, rotation of the gear 21 by movementof the carriage to carry the cutter across the face of -the blank willcause a correct rotation of the cutter for Archimedian spiral gearteeth. If, however, a different spiral is desired, the rack 22 shouldbegiven a longitudinal movement to effect the desired rotation of thecutter.

`As. shown, this is accomplished by anarrangement whereby the movementof the Carriage on the ways on whichiit is mounted causes a.longitudinal movement of the rack on its ways 26. A pin 27 projectingdownwardly from the rack engagesa'slot in the arm 28 of a bell cranklever pivoted at 30 and' the arm 3l of the samelever engages a cam 32mounted on the carriage and movable therewith. The cani is designed inaccordance with the particular spiral of the gear to be cut.

The operation of the compound driving mechanism will best be understoodfrom the following analysis. If the cutter spindle carriage isstationary and the gear blank and cutter rotated the cutter 6 Willberotated in meshing timed relation by the worm 19 and Worm wheel 178, therack engaging gear 2l remaining stationary; but ifthe completely cutiinished'gear `is held stationary and the cutter spindle carriage movedto lcarry the cutter across the face of the gear, the rack 22vand gear2l willcause a suitable meshing rotation of the cutter 6 as it traversesthe face of the gear, the worm Wheel 18 remaining stationary. Itfollows, therefore, that during the cutting operation the desiredrotation of the cutter relative to the blank Will be maintained whetherthe carriage is moved at a uniform rate asrby the feed screw 35 or by acam giving a variable speedmovement.

It will be 'understood' that the foregoing particular description 'isillustrative merely and that the invention may be variously Vembodied.

I claim: Y l. In a machine for cutting spiral bevel gears, incombination',- a rotatablecutter, a

movable carriage in whichsaid cutter is vro-V f tatably mounted formovement across the face of a gear blank, and means for rotating thecutter comprising a diterential mechanism and two actuating means fordriving the diterential mechanism, one of said actuating meanscomprising a relatively stationary rack and a'pinion mounted on thecarriageY and engaging said rack for actuation of the pinion during themovement of the carriage. 2. In a machine for cutting spiral bevelgears, in combination, a rotatable cutter, a movable carriage in whichsaid cutter is -rotatably mounted for movement across the face ot a gearblank, and means forretating the cutter comprising a diierentialmee'hanism and twoactuating means for driving the diii'erentialmechanism, one of said actuating means comprising a relativelystationary rack and a pinion mounted on the carriage and engaging therack together with meansyfor giving the rack a limited longitudinalmovement during movement of the carriage.

3. In a machine for cutting spiral bevel gears, in combination,afrotatable cutter, a movable carriage in which said cutter is rotatablymounted for movement across the face of a'gear blank, and means forrotating the cutter comprising a diiiierential mechanism and twoactuating means for driving the differential mechanism, one of saidactuating means comprising a relatively stationary rack, a pinionmounted on said carriage and engaging therack, a cani` mounted on thecarriageandl means controlled by the cam tor moving the racklongitudinally.

4. Ina machine of the class described a cutter, means for shifting saidcutter bodily, means for simultaneously rotating said cutter about itsown aXis, a plurality of independent driving means for said secondmentioned means adapted to produce their combined effect thereon, andacommon operating mechanism for said first mentioned means and saiddrivingmeana one of said driving means being controlled by a cam. VIntestimony whereof, I havev signed my name to this specificationV this8th day of March, 1929. y

- ERNEST L. FICKET'I.-V

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